Cathode-ray tube sweep circuit



July 22, 1952 v. 0. WILSON CATHODE-RAY TUBE SWEEP CIRCUIT Filed Oct. 11, 1945 IBK.

INVENTOR. VOLNEY C. WILSON Amansv Patented July 22, 1952 UNITED STATES CATHODE-RAY TUBE SWEEP CIRCUIT Volney C. Wilson, Santa Fe, N. Mex., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy 7 Application October 11, 1945, Serial No. 621,836.

'7 Claims. I

The present invention relates to radio echo detection apparatus and more particularly to a circuit for providing a radial sweep on the oathode ray tube indicator thereof, so as to cause the same to furnish a presentation characterizing the cathode ray tube indicator as a Plan Position Indicator.

One such circuit is disclosed in copoending application Serial 594,044, filed May 16, 1945 for Radio Echo Detection System by James F. Koehler. In that circuit the radial and rotating sweep by the electron beam of the cathode ray tube indicator is provided by varying the amplitude of a sawtooth wave voltage, sinusoidally in two parts 90 out of phase by means of a rotary two-phase transformer.

An object of the present invention is to provide a circuit corresponding to that disclosed in the aforesaid patent application, wherein the sinusoidal variations in-the amplitude of a sawtooth wave voltage are obtained by applying it to a three-phase rotary transformer.

This and other objects will be apparent from the following specification. when taken with the accompanying drawing comprising a circuit diagram disclosing the invention.

In the drawing, a rotary three-phase transformer I is providedwitha rotatable primary winding 2 and secondary windings 3, 4, and 5. One end of the'primary winding Zis connected to a suitable source of voltage having a sawtooth wave form 6. Thesawtooth wave voltage is generated in any suitable manner such as disclosed in the aforesaid copending application. Also the leading edge of the sawtooth voltage wave form '6 may be provided with a pip l by some suitable means such as disclosed in said application to charge capacities-existing in the leads to the winding 2' and in the winding 2 itself. The other end of the" winding 2 is connected to a suitable source 8 'of'po'sitive potential.

The secondary-windings 3-, 4 and 5 are connected in Y;forination as'indicated, and the arrangement is such that the'windings produce maximum voltages at 120 spacing of the rotary winding 2. The ends of the secondary windings 3, 4 and 5 are connected to three resistors [0, H and I2 respectively, also connected together in Y formation. A point' l3 of the resistor 12 is connected to ground, this .point beingselected so as to make the ends oif'the resistors l0 and H 90 apart electrically-instead of 120. The voltagesproduced at the outerlends of thfe resistors and I l are used to control the deflection plates of the cathode ray tube indicator hereinafter described. 7

The voltages at the outer ends of the resistors l0 and H cannot be connected directly to the opposed deflection plates respectively of the hereinafter described cathode ray tube'indicator for a push-pull operation since they are single-ended outputs. To overcome this diniculty a circuit comprising electron tubes Hi and I5 is provided. The electron tube 14 is provided with a cathode [6, control grid l1 and anode it while the tube I5 is providedwith a cathode I9, a control grid 20 and an anode 2|. The voltage at the outer end of the resistor H3 being in the form of a sawtooth wave having a sinusoidally varying amplitude is connected to the control grid I! of the electron tube M. The grid H is connected to ground through resistors 24 and 25. The juncture of the resistors and 25 is connected to ground through a capacitor 26. The same juncture is also connected to the movable arm 2'! of the potentiometer 28. One end of'the potentiometer 28 is connected to a positive source of voltage 29 and the other end of the potentiometer 28 is connected to ground.

The cathode l6 of the tube I l is connected to ground through a resistor 30, and the anode I8 is connected to a source 3| of positive potential through a load resistor 32. The anode I8 is also connected to the control grid 34 of a power beam amplifying tube 35 the output of which is connected to a deflection plate 35 of a cathoderay tube indicator 31.. v.

The control grid 20 of the electron tube i5 is connected to ground while the cathode 19 thereof is connected to the cathode it of the tube Hi. The anode of the tube [5 is connected to a source 38 of a positive potential through a suitable load resistor 39. .The anode 21 is connected to the control grid 40 of a power beam amplifier M the output of which is connected to .a deflection plate 42 opposite the. deflection plate 35 0f the cathode ray tube indicator 31 Thus'the two anodes l3 and 2! furnish the deflecting voltages for the vertical deflecting plates 36 and 52' of the cathode ray tube indicator 31.

' In order for the circuit to operate as desired the characteristics of the tubes [4 and [5 should, be substantially the same and the resistors-32 and 39 substantially equal'in value. Also the value of the resistor 30 should be such that when multiplied by the amplification factorofv orient the tubes M or 15 the product will be much greater than the sum of the plate resistance of one of the tubes plus the load resistance of that tube.

The horizontal deflection plates 50 and of the cathode ray tube indicator 31 are connected respectively to anodes 52 and 53 of power beam amplifying tubes 54 and 55. The screen grids of the tubes 52, 53. 4| and 35 are connected together and to a source 56 of positive potential. The cathodes of the tubes 54, 55, 4| and 35 are connected respectively through resistances 51, 58, 59 and 66 to a common lead 6| which is connected through a resistance 62 to ground. The anodes of the tubes 54, 55, 4| and 35 are connected through resistors 65, 66, '61 and 68 respectively to the source 56 of positive potential to provide operating potentials.

The phase inversion circuit disclosed in the upper portion of the drawing for furnishing pushpull potentials from the outer end of the resistor H) for energizing the vertical deflecting plates 42 and 36 of 'the cathode ray-indicator 3'! is duplicated by a circuit, not shown, for energizing the horizontal deflecting plates 5| and 5|] of the cathode ray tube indicator 31 from the output 69 at the end of the resistor In the operation of the circuits described above and shown in the drawings the sawtooth wave from the rotary transformer I, as taken from the outer end of the resistor I6, is applied to the grid [1 of the tube M. The potentiometer 28 is adjusted so that current will normally flow in both tubes l4 and I5. The current in the tube I4 will then increase as the voltage of the sawtooth wave rises. 'Since no voltage is applied to the grid of the tube l5, this tube would normally not be affected by the signal. However, the two cathodes l6 and I9 are connected together and through the resistor 30 to ground, and therefore the current flowing in the tube l4 passes through the resistor 30 and raises the potential of the cathode |6 because of the voltage drop through the resistor 36. This also raises the potential of the cathode I9 which therefore becomes less negative with respect to the grid 20 in proportion to the signal applied on the grid oi. the tube M. The potentialon the'cathodes l6 and I9 corresponds to about one-half of the'signal potential. This causes the potential of the anode l8 of the tube l4 as'the current increases in that tube, to swing in a negative direction through an-amount proportional to one-half of the signal applied to the grid while the potential of the anode 2| of the tube l5 will swing in a positive direction through substantially the same amount as the current is. reduced in that tube due to the increase involtage of the cathode l9 thereof. Thus, sawtooth voltage waves opposite in phase appear on the anodes I8 and 2| of the tubes'M and I5 respectively and thus may be applied to the amplifiers 4| and respectively feeding the vertical deflecting plates 42 and 36 of the cathode ray indicator tube 31. The signals from these tubes l4 and I5 will be equal in amplitude but opposite in phase and the amplitude will vary sinusoidally as thev rotary primary of the rotary transformer rotates.

Itis not necessaryto produce a deflection of V 4 the electron beam of the cathode ray tube indicator 31 by applying deflection voltages in pushpulL arrangement. A sawtooth voltage suflicient to deflect the electron beam may be applied to one horizontal and one vertical electrode deflection plate, the others being kept at constant voltages. .In such acase, however, the difference between the-maximum voltage applied to the plate and the other elements of the cathode ray tube is much greater than the case where the deflection voltages are applied to the deflection plates in push-pull. There may be a tendency for these high voltage differences to interfere with the functioning of the electron beam and hence I prefer to use the push-pull arrangement. While I have not shown a clamping arrangement for starting each electron beam sweep from the same point on the indicator 31, it is to be understood that such an arrangement, for example, as disclosed in aforesaid patent application, may be used. Having thus described. my invention what I desire to secure by Letters Patent and claim is. 1

1. In aradio echo detection system a circuit for producing a.plan'position'indicator scan comprising a three-'phase'rotary transformer having a rotating primary winding and three Y connected secondary windings, three Y connected resistors, conductors'connecting the outer end of said resistors to the outer end of said secondary windings respectively, means for, grounding an intermediate portion of one of said resistors-so as to provide the output voltages from the other of said two resistors 90"; electrically out of phase, means to split the output from at least one of said last-named resistors into two parts l out of phase, a cathode day tube indicator having op-'- posing deflection plates, and means to apply-said out of phase outputin push-pull to'op'p'osin'g deflection plates of said cathode ray tube indicator.

2. A circuit for providing a plan position'indicator sweep on a "cathode ray tube indicator com prising means for furnishing a sawtooth wave form voltage, a rotarytransformer' for sinusoidally varyingthe amplitude of said saw-tooth voltage, means for providing two out of phase voltages from said transformer, means to divide each of said last-named voltages into two apart voltages and means for applying one set of said 180- apart voltages to the horizontal deflecting plates of a cathode ray indicator and the other set of 180 apart voltagesito the vertical deflecting plates of a cathode' ray tube indicator. Y 3. In a circuit of the character describeda three-phase rotary transformer having a rotary primary-winding and three Y connective sec.-

ondary windings, three Y connective resistors one corresponding to each of said secondary windings, conductors connecting the ends of said windings and resistors respectively, a ground connection at an intermediate point of one of said resistors'to provide a predetermined phase difference -"in the voltages at the outer end of the other two of said resistors, a cathode rayindicator, and means for applying said voltages to said indicator to deflect the electron beam thereof.

4. In a radiorecho detectionsystem, a circuit for producing a plan position indicator scan comprising a substantially symmetricalthree-pha'se rotary transformer, twooutput circuits from said transformer, means to reduce the normal phase difi'erence between, said outputs to provide driving circuits 90 apart, means to split the phase of said driving circuits respectively to produce pushpull outputs, a cathode ray tube indicator, and

means to apply said push-pull outputs to said indicator to cause a sweeping by the electron beam thereof.

5. In a radio echo detection system, a circuit for producing a plan position indicator scan comprising, a source of sawtooth wave form voltage, a three-phase rotary transformer having a rotary primary winding and three Y-connected secondary windings, three Y-connected resistors, one corresponding to each of said secondary windings, conductors connecting the ends of said windings and resistors respectively, means for energizing the rotary primary of said transformer from said source, a ground connection at an intermediate point on one of said resistors to provide a predetermined phase difference in the voltages at the outer end of the other two of said resistors, a cathode ray indicator, and means for applying said last-mentioned voltages to said indicator to deflect the electron beam thereof.

6. A circuit for providing a plan position indicator sweep on a cathode ray indicator comprising, a source of a sawtooth wave form voltage, a three-phase rotary transformer having a rotating primary winding and three Y-connected secondary windings, means for energizing said primary winding from said source, three Y-connected resistors, conductors connecting the output end of said resistors to the outer end of said 6 of said 180 apart voltages to the horizontal deflecting plates of said indicator and the other set of 180 apart voltages to the vertical deflecting plates of a cathode ray indicator.

7. A circuit for providing a plan position indicator sweep on a cathode ray indicator comprising, a source of a sawtooth Wave form voltage, a three-phase rotary transformer having a rotating primary winding, and three Y-connected secondary windings, means for energizing said primary winding from said source, three Y-connected resistors, conductors connecting the outer end of said resistors to the outer end of said secondary windings, respectively, means for grounding 'an intermediate portion of one of said resistors so as to provide the output voltages from the other of said two resistors electrically out of phase, an electron tube phase inverting circuit responsive to each of said last-named voltages to obtain two sets of voltages, each having a pair of voltages differing in phase by and means for applying one set of said 180 apart voltages to the horizontal deflecting plates of said indicator and the other set of 180 apart voltages to the vertical deflecting plates of said indicator.

VOLNEY 0. WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 725,092 Kelly et al Apr. 14, 1903 2,001,465 Klinkhamer May 14, 1935 2,135,171 Chireix Nov. 1, 1938 Pooh ':'."-'.'-7-* 

